The present invention is concerned with structures useful for environmental enhancement and with the method of their manufacture. The structures are advantageously made from small, low value logs such as thinnings or tree tops.
Organic debris is generally recognized as important for maintaining the biotic and abiotic functions of streams, lakes, and ponds. In streams, large woody debris has a major influence on channel form and on sediment transport and deposit patterns. The quantity of large woody debris is highly correlated with the number of pools that are critical as fish habitat. In addition to providing favorable water conditions for aquatic life, this in stream wood also provides shade and refuge from predators.
An earlier patent of one of the present inventors, U.S. Pat. No. 5,823,710, describes a substitute for natural large woody debris that can be readily manufactured and transported to the site where it will be used. This product has proved very effective for managing stream habitat and hydrology. It is formed as a hollow, generally cylindrical or frustroconical structure formed from an even number of small logs held together by wood struts mortised into the logs. The central portion may be ballasted with rocks to increase the weight and stability against movement by high water.
While the above noted product has been excellent for streams, lakes and ponds present their own unique needs for woody debris. In particular, structures suitable as perches for birds and basking surfaces for amphibians and turtles are essential to the general environmental health. As one example, the western pond turtle (Clemmys marmorata) is presently a threatened species. This once abundant turtle has been in serious decline through a combination of factors including habitat loss and predation by non-native species. These turtles require a significant basking time in sunlight in order to regulate body temperature. Adequate basking time also appears to be linked to reproductive success of females. The turtles prefer an environment with large amounts of emergent logs or boulders in areas of maximum sunlight availability. Underwater woody debris close to basking sites provides hiding places from predators. Crevices under sunken logs are especially preferred. The present invention can fill this need for birds, turtles, and other aquatic species since it can be readily assembled and optimally placed, both on the surface and under water.
The present invention is an engineered wood structure that can be placed in an aquatic environment to fill the need for surface resting places for various aquatic and avian species. It can also be used to provide underwater refugia when anchored below the surface. The structure can be readily assembled on site, if necessary, using a number of small logs that can often be obtained locally. A number of the logs are placed side-by-side to form a deck surface. A single log is spaced apart from and centered below the deck logs to serve in the manner of a keel for the structure. The deck logs and the keel log are connected by struts. At least two spaced apart struts depend from the lower surface of each of the deck logs and are connected into the keel log.
While the invention is primarily directed to the use of small logs or other woody material, it should be considered more broadly so as to include other materials such as pipe or tubes of metal or plastic materials. When the term xe2x80x9clogsxe2x80x9d used it should be considered to encompass these alternative elongated materials.
The upper surface of the side-by-side deck logs may be configured to describe a plane, the arc of a circle, the major curvature of an ellipse, or other suitable geometric configuration. The major surface of an ellipse would be defined as that in which a line drawn through the transverse center point of the deck logs and the keel log would lie along the minor radius of the ellipse.
The deck logs may lie against and be touching each other or they may be spaced apart, depending on the particular need that the structure will fill.
It should be noted that the terms xe2x80x9cupper and lower surfacesxe2x80x9d of the deck logs and xe2x80x9cdeck and keel portionsxe2x80x9d are relative. They refer to the configuration in which the structure would most usually be used and serve for convenience in description. However, there may be occasions when the structure would be inverted or otherwise positioned in use and during assembly.
A preferred method of joining the deck and keel logs is by the use of wood struts mortised into the logs. Where materials other than wood are used other methods of fastening might be more suitable, such as welding or sleeved fittings. The ends of the deck logs may be evenly arranged or somewhat displaced from each other.
The easiest construction to make is that in which the upper surface of the deck logs defines the arc of a circle since the struts are then all of equal length. However, in the case of a floating structure this presents the minimum width of deck area. This is a problem noted with the structure of U.S. Pat. No. 5,823,710. Other configurations including planar and elliptical (in cross section) deck surfaces which give a greater exposed area may be preferred.
The number of logs in the deck portion is not critical and may vary between as few as two or as many as 12. Normally between about three to eight deck logs are preferred. Length and diameter of these logs is not critical. Lengths will normally be between in the range from about 2-4 m (xcx9c6-13 feet) and diameters between 10-20 cm (4-8 inches). There may be either an even or odd number of deck logs. Keel logs will fall within the same size range. Length and diameter of the struts is likewise not critical. Typically the struts will be somewhat smaller in diameter than the deck or keel logs. About 6-10 cm (xcx9c2xc2xd-4 inches) in diameter would be typical. Lengths will usually be in the range of about 30-60 cm (1-2 feet).
The structure need not be used only in the configuration of a floating raft. One end may be anchored under water so that the other end is elevated above the surface for some distance. This arrangement is particularly useful since it presents an favorable perch for birds. The angle made with the water surface may be very low or, in the extreme, the long dimention of the structure may be normal to the surface. Alternatively, the entire structure may be held below water. The structure may be used in a manner where it is entirely surrounded by water or it may be adjacent a bank of the lake, pond, or stream where it is deployed.
It is an object of the present invention to provide an engineered wood structure that can be used in various manners for environmental enhancement.
It is another object to provide a structure for use in streams, lakes, and ponds that provides a basking surface or refuge for avian and aquatic fauna.
It is a further object to provide a structure of the above type that may be readily assembled from small logs or other woody material that is environmentally friendly and natural in appearance.
These and many other objects will become readily apparent when reading the following detailed description taken in conjunction with the drawings.